2020-03-16 实现简易版 EventEmitter

[fanmingfei]

const ee = new EventEmitter()
// 绑定事件
ee.on('someAction', (a, b, c) => {
  console.log('action1',a,b,c)
)

// 绑定事件
ee.on('someAction', (a, b, c)=>{
  console.log('action2', a, b, c)
})

// 绑定单次事件
ee.once('someAction', (a, b, c)=> {
  console.log('actionOnce', a, b, c)
})

// 触发事件
ee.emit('someAction', 1, 2, 3)
// 输出 action1 1 2 3
// 输出 action2 1 2 3
// acitonOnce 1 2 3

// 再次触发事件
ee.emit('someAction', 3,4,5)
// 输出 action1 3 4 5
// 输出 action2 3 4 5

[Vince-9]

class EventEmitter {
  constructor() {
    this.evePool = [];
  }

  on(e, cb) {
    if (!this.evePool[e]) this.evePool[e] = [];
    this.evePool[e].push(cb);
  }

  once(e, cb) {
    if (!this.evePool[e]) this.evePool[e] = [];
    const fn = (...args) => {
      cb(...args);
      this.evePool[e] = this.evePool[e].filter(f => f !== fn);
    }
    this.evePool[e].push(fn);
  }

  emit(e, ...args) {
    if (this.evePool[e])
      this.evePool[e].forEach(cb => {
        cb(...args);
      });
  }
}

[wangshouren7]

class EventEmitter {
    constructor() {
        this.events = Object.create(null);
    }
    on(key, handler) {

        (this.events[key] || (this.events[key] = [])).push(handler);
    }
    once(key, handler) {

        const _handler = (...args) => {
            handler(...args);
            this.off(key, _handler)
        }

        (this.events[key] || (this.events[key] = [])).push(_handler);
    }
    off(key, handler) {
        const events = this.events[key];
        if (events) {
            this.events[key] = events.filter(h => h !== handler);
        }

    }
    emit(key, ...args) {
        const  _events = this.events[key];

        if (_events) {
            _events.forEach(h => h(...args));
        }
    }
}

[LiZhaji]

class EventEmitter{
  _cache = {}
  _onceCache = {}
  on(key, callback){
    const events =  this._cache[key] = this._cache[key]?.length ? this._cache[key] : []
    events.push(callback)
  }
  once(key, callback){
    const events =  this._onceCache[key] = this._onceCache[key]?.length ? this._onceCache[key] : []
    events.push(callback)
  }
  emit(key, ...args){
    this._cache[key].forEach(event => event(...args))
    this._onceCache[key]?.length && this._onceCache[key].forEach(event => event(...args))
    this._onceCache[key] = []

  }
}

[markmcsong]

class EventEmitter {
  constructor() {
    this.events = []
  }
  on(ev, callback) {
    if (!this.events[ev]) this.events[ev] = []
    this.events[ev].push(callback)
  }
  once(ev, callback) {
    // 执行完解除绑定(包装处理)
    const wrapCb = (...args) => { 
      callback.apply(null, args)
      this.off(ev, wrapCb)
    }
    this.on(ev, wrapCb)
  }
  off(ev, callback) {
    this.events[ev] = this.events[ev] && this.events[ev].filter(fn => fn !== callback)
  }
  emit(ev, ...args) {
    this.events[ev] && this.events[ev].forEach(fn => fn.apply(null, args))
  }
}